Testing of concrete by laser ablation

Abstract

A method of testing concrete in a structure in situ, by: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete; detecting a characteristic of energy which has been transferred to the concrete; determining, separately from the detecting step, the total quantity of concrete removed by the succession of pulses; and calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed.

What is claimed is: 
     
       1. A method of testing concrete in a structure in situ, comprising: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete;   detecting a characteristic of energy which has been transferred to the concrete;   determining, separately from said detecting step, the total quantity of concrete removed by the succession of pulses; and   calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed.   
     
     
       2. A method as defined in claim 1 wherein the laser radiation has an energy density and wavelength selected to transfer energy to the concrete in order to effect vaporization of a portion of the concrete and the step of determining comprises detecting radiation emitted by concrete which is vaporized by the laser radiation and performing spectral analysis on the detected radiation. 
     
     
       3. A method as defined in claim 2 wherein the property calculated in said calculating step is the strength of the concrete. 
     
     
       4. A method as defined in claim 2 wherein the property calculated in said calculating step is the physical state of the concrete. 
     
     
       5. A method as defined in claim 2 wherein the concrete contains cement, sand and aggregate, the cement containing finely ground solid material, the concrete having a solid material/sand volume ratio and one property calculated in said calculation step is the solid material/sand ratio. 
     
     
       6. A method as defined in claim 5 wherein a second property calculated in said calculating step is a characteristic of the aggregate. 
     
     
       7. A method as defined in claim 2 wherein the concrete contains cement, sand and aggregate, the cement containing finely ground solid material which has a chemical composition and one property calculated in said calculation step is the chemical composition of the finely ground solid material. 
     
     
       8. A method as defined in claim 7 wherein a second property calculated in said calculating step is a characteristic of the aggregate. 
     
     
       9. A method as defined in claim 2 wherein the concrete contains aggregate having a given size and dispersed throughout the concrete, and one property calculated in said calculating step is a characteristic of the aggregate. 
     
     
       10. A method as defined in claim 9 wherein the characteristic is the size of the aggregate. 
     
     
       11. A method as defined in claim 9 wherein the characteristic is the uniformity of dispersal of the aggregate throughout the concrete. 
     
     
       12. A method as defined in claim 1 wherein the energy transferred to the concrete has the form of acoustic waves. 
     
     
       13. A method as defined in claim 12 wherein the property is the physical state of the concrete.